I love the WarPG 2nd Edition source books. They are always written with a stunningly grounded and coherent tone that really helps the world and the setting come to life.
This book is no exception, in that it does a wonderful job getting into the nitty gritty about Chaos in the Old World, and most importantly, delving into the details that a cursory understanding of the setting might overlook.

As an example, in discussing the cults of Chaos, the book talks about the worship of Slaanesh, and how or why one might fall under his sway. The average gamer, slightly familiar with the setting, will know Slaanesh as "the perverted God", who's all about drugs, sex, and rock and roll.
The Tome of Corruption dismisses that theory, and details each of the Gods as a fleshed-out and understandable concept, which could serve as a believable point of worship for characters who don't have to be cartoon evil.

That's the best thing this book does. It discusses corruption, chaos, and the dark arts as something born out of real and believable events and concepts, and not as the cartoon enemies that they can easily be turned into. Chaos here is layered and 'realistic'. For that reason alone, I think that this book is a necessity for any GM running a campaign of WarPG. To have that understanding of Chaos will help you create motivated villains that feel even sympathetic, in some ways, rather than always having to rely on the evil cultist or beastman who just wants destruction for its own sake.

The book is a real variety show of material, from new careers, relics, plot hooks, sample cults, and even a mutation chart that requires you to roll a d1000...

My biggest complaint about this book is that like Chaos itself, it's almost incoherent in places. There were clearly deadlines looming here, because the book is rife with typos, repeated sentences, and even some formatting errors in some parts where paragraphs are switched around between subsections.
Not enough to make the book unusable, but definitely noticeable enough to dock a point from it.

I have read most if not ALL the books about Chaos in Warhammer Fantasy. I read the two tomes of Realms of Chaos. I also read Complete Liber Chaotica, WHFB Beast of Chaos and WHFB Hordes of Chaos. This one is by far the most complete on the topic and the most pleasant and interesting to read followed closely by Complete Liber Chaotica. I cannot recommand you this book enough for every fan of Warhammer Fantasy (RPG players or NOT). Even the readers interested by Fantastic universe could find this reading interesting.

Tome of Corruption add also a lot of new content concerning Chaos that have never been written so far in other Warhammer books. It push the topic much more further and embrace it widely. It cover in detail many old and new aspects.

You will find in this book the following chapters:

A first Part: The Enemy Within

1- Chaos in the Old World

2- The lost and the damned

3- Catalogue of Change (MORE than 150 mutations. A general random table and 4 random tables adapted for each Chaos Gods.)

4- Cults of Chaos (It feature also cultist career for each four Chaos Gods)

5- Objects of Chaos

A second Part: Shadows of Chaos

6- The Places between: Life in the wilderness

7- Beasts of Chaos (and the template to play one as PC...)

8- Menagerie of the Strange

9- Defenders of the Empire (Some words about the Witch Hunters and the other enemies of Chaos)

Part III: The Chaos Wastes

10- The Chaos Wastes (The Landscape of Chaos)

11- Norsca (The Norsca region and his folks and their culture are explain in details. Template are given to play a norse and specific career related to norse people are also offered.)

12- Hordes of Chaos (A distinction is made between the Norsemen and the other people who follow more directly and specificaly the Chaos Gods. Template are presented to play a men of the Hordes of Chaos such as the Kurgan)

13- Slaves to Darkness (This chapter have the following section that every Chaos worshiper is looking for: Champion of Chaos, Chaos Sorcerers, Rewards of Chaos, Retinues. Basicly, this section explain the path followed by those who worship the Chaos Gods. It give the career associated to this path and the advantages and dangers it represent.)

14- Chaos Armory

Part IV: Realm of Chaos

15- The Ruinous powers (The four Gods of Chaos)

16- Beyond the Wastes of Chaos (Walk toward the Eye like no other book have brought you before. Then enter into the Realms of Chaos themselves. Sanity is for the weaks!)

18- Legion of Chaos (The stats blocks about the Major and Lesser Chaos Gods Daemons... Your player will be able to fight for the best and the worst the Bloodthirster, the Keepers of Secrets, the Horror of Tzeentch and all the other classic Daemons commonly associated to the Chaos Gods. This section also explain how to design your own new Daemons and give you the proper random table to build them)